Disposable external fixation device

ABSTRACT

The invention relates to a novel disposable axial external fixation device for reducing bone fractures, of the type comprising an extendible rod-like middle body ( 2 ) and oppositely located bone screw clamps ( 5, 6 ) which are articulated to the respective ends ( 3, 4 ) of the rod like middle body ( 2 ) by means of ball joints. Advantageously, a ball-and-socket joint ( 16 ) is mounted to each clamp ( 5, 6 ), within a main body ( 20 ) with which means ( 25, 26, 21, 22, 23 ) for clamping bone screws clamping is associated or co-operates. It is also provided an ancillary member ( 30 ) adapted for releasable association with one end of each clamp ( 5, 6 ) to better adapt each clamp for use in different conditions of installation of the fixation device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0001] In the drawings:

[0002]FIG. 1 shows a vertical perspective view of an axial unilateralexternal fixation device according to this invention;

[0003]FIG. 2 shows an exploded perspective view of the fixation deviceshown in FIG. 1;

[0004]FIG. 3 shows a further sectional view of a bone screw clamp of thefixation device according to the invention;

[0005]FIGS. 4 and 5 show sectional schematic views of a detail of theclamp in FIG. 3 in two different conditions of its operation.

DETAILED DESCRIPTION

[0006] With reference to the drawing views, an axial unilateral externalfixation device for reducing bone fractures in orthopedic surgery,realized according to the present invention, is totally shown at 1.

[0007] The fixation device 1 comprises a rod-like middle body 2 havingan axis x-x, and having opposite ends 3, 4 which are articulated to therespective bone screw clamps 5, 6.

[0008] Advantageously, both the rod-like middle body 2 and the clamps 5,6 are made out of a transparent material to X-radiation, such as apolyetherketone plastics matrix known as “Peek”, which is reinforcedwith a predetermined amount of carbon fibers in order to obtain asuitable rigidity.

[0009] More particularly, the rod-like middle body 2 is axiallyextendible since it is formed by a first 8 and a second 9 mating partsof prismatic shape. The parts 8 and 9 telescopically slide on eachother.

[0010] Each of said parts 8, 9 comprises a first portion 8′, 9′ ofelongate semicylindrical shape which is integrally formed with a secondcylindrical end portion 8″, 9″ of short length. Each part, 8 and 9, istherefore L-shaped if seen sideways.

[0011] The semicylindrical portions 8′, 9′ are coupled to each other ina sliding manner by means of a driving groove 7, longitudinally formedin the portion 8′, and a corresponding slide 7′ longitudinally formed inthe other portion 9′. In particular, the portion 8′ essentially has aC-shaped section, while the other portion 9′ comprises a longitudinalrib having a T-shaped section to define said slide 7′.

[0012] Of course, other driving/sliding combinations can be foreseenwithout coming out of the scope of the invention.

[0013] Advantageously, means for stopping said parts 8 and 9 in theirsliding movement is provided.

[0014] This stop means comprises a locking screw 11, perpendicularlyextended to the axis x-x, which locking screw has a threaded end portion12 engaged in a threaded hole 13 formed in the slideway 7′. In addition,the portion 8′ of the part 8 is formed with a clearance slot 10 whichlongitudinally spans most of the portion 8, as shown in FIG. 2. Thescrew 11 goes through the slot 10, preferably with a smooth section ofits shank 14, to ease the sliding movement of the portions 8 and 9 oneach other.

[0015] The screw 11 is a socket head screw (Allen screw) for convenientoperation with a wrench.

[0016] By loosening and tightening the screw 11, the extension of therod-like middle body 2 of the fixator 1 can be adjusted as necessary,depending on the different dimensions of the broken bone. On thecontrary, no rotations of the parts 8 and 9 about the axis of therod-like middle body 2 occur, because of the C- and T-shaped sections ofthe driving groove and of the slide.

[0017] In the compact setting of the rod-like middle body 2, theportions 8′ and 9′ of the parts 8 and 9 are fully superposed, with oneabutting the cylindrical end portion 9″, 8″ of the other.

[0018] As mentioned above, the opposite ends 3, 4 of the rod-like middlebody 2 are articulated to the respective clamps 5, 6 of the bone screwsby means of ball joints.

[0019] Each joint comprises a ball-and-socket joint 16 mounted to eachclamp 5, 6.

[0020] In particular the ball-and-socket joint 16 includes a cylindricalsocket 17 which is delimited by a ball-retaining rim 17 a and providedin each clamp 5, 6, and a ball head 18 lodged in the socket 17. The ballhead 18 has a shank 19 adapted to be received in a corresponding socket15 on each of the ends 3, 4 of the rod-like middle body 2.

[0021] The socket 15 lodging the shank 19 is formed near-centrally inthe end portions 8″ and 9″ of the parts 8 and 9. Briefly, the socket 15lies along the axis x-x, and the shank 19 is held in the socket 15 by areleasable locking means, such as a lockpin 27 passing through a hole 28formed transversal to the axis x-x in the portion 8″, and acorresponding hole 28′ transversal to the shank 19.

[0022] Each of the clamps 5 and 6 comprises a main body 20,substantially prismatic in shape, wherein the cylindrical socket 17,which lodges the ball head 18, is formed.

[0023] A side flange 26 is removably associated with the main body 20for constraining the clamp onto bone screws, in the example two screws21 lying in a plane parallel to the lying plane of the axis x-x, andbeing placed a predetermined distance away therefrom.

[0024] More particularly, the main body 20 has a side wall 25 of shapedcontour. The contour of the flange 26 substantially mates with the sidewall 25, such that the side wall 25 and the flange 26 will joint likethe jaws of a vise, so locking the bone screws.

[0025] Preferably, the removable coupling of the body 20 and the flange26 occurs by means of the engagement of a pair of screws 21 incorresponding threaded seats 22 provided in the main body 20, throughclearance holes 23 in the flange 26. The threaded seats 22 are formed inthe side wall 25 of the body 20.

[0026] This particular configuration enables the bone screws to be heldin the clamp substantially alongside the ball-and-socket joint, therebyachieving a highly compact structure of the overall clamp.

[0027] Advantageously, locking means 40 of the ball-and-socket joint 16in a selected angular position is also provided. This locking means 40comprises a slider 41 which is guided for movement inside thecylindrical socket 17 of the main body 20 in the direction toward theball head 18, by the action of a driving means 42.

[0028] This driving means 42 comprises a shaft 47 which transverselyextends to the socket 17 and is provided with a cam 47 a acting on theslider 41. The shaft 47 can be manually rotated with a suitable wrench,and is purposely formed with a recessed hexagon 43 at an accessible endthereof.

[0029] Specifically, the slider 41 is formed with a cylindrical rimhaving a plurality of contrate teeth 44, i.e. all extending towards thesame direction parallel to the axis of the rim. These teeth 44 areintended to bite into the surface of the ball head 18, upon actuation ofthe driving means 42, and form a plurality of impressions of a suitabledepth therein, e.g. a few tenths of a millimeter deep. In this way, theball head 18 becomes set permanently, and the ball-and-socket joint 16is practically locked in a positive manner.

[0030] A stroke limiting means 45 of the slider 41 is provided so thatthe teeth 44 bite a predetermined depth into the ball head 18. Thislimiting means 45 comprises a radial nose 46 formed integrally with theshaft 47 and appearing externally of the main body 20, which is arrangedto abut against a stop 48 formed on the main body 20, at an appropriateangular setting of the shaft 47 relative to the main body 20.

[0031] With the radial nose 46 abutting the stop 48, the plurality ofteeth 44 of the slider 41 will have sunk the maximum anticipated depthinto the surface of the ball head.

[0032] In assembling one of the clamps, 5 or 6, first the ball head 18of the joint 16 is inserted into the cylindrical socket 17 with theshank 19 abutting out of the main body 20. Then the slider 41 with itsteeth 44 facing the ball head 18, and finally the shaft 47 to stop theprevious parts from coming off, is assembled. The shaft 47 is positionedsuch that an end portion of the cylindrical socket 17 is left availablefor receiving an additional cylindrical member as described hereinbelow.

[0033] The cylindrical socket 17 at the free end of the main body 20 isalso used for holding an ancillary member 30 which effectively makes theclamp, 5 or 6 more versatile, depending on the different installationsof the fixation device.

[0034] For example, an ancillary member 30 is illustrated in thedrawings by a T-connection member 31, for connecting the clamp 5 to aring of a ring fixator known in the art as the Ilizarov system.

[0035] The connecting member 31 comprises a cylindrical shank 32pivotally fitted in the same cylindrical socket 17 that accommodates theball head 18 of the ball-and-socket joint 16.

[0036] A locking screw 29 engages in a threaded hole 29′, transverselyformed at the shank 32 and through a slotted hole provided in the mainbody 20 close to the end thereof opposite to the ball joint 16. Theconnecting member 31 further comprises a plate-like portion 33 which isintegrally formed with the shank 32 and perpendicularly extends to it.This portion 33 has oppositely located flanges which are penetrated byslotted holes 34 for connection to a ring of an external fixation deviceof the Ilizarov system.

[0037] In this way, a clamp 5 or 6 provided with the connecting member31 can be fastened to a ring of the Ilizarov system to produce aso-called “hybrid splint”, that is an external fixation devicecomprising an axial fixator and at least one ring, so combining theadvantageous features of ring fixation devices and unilateral axialfixation devices.

[0038] Another ancillary member 30 is illustrated in the drawings by ametaphysis clamp 35 for clamping to bone screws which lie in a planesubstantially perpendicular to the axis x-x and, therefore, transversalto the lying plane containing said bone screws held between the walls 25and 26 of the clamps 5 or 6.

[0039] More particularly, a metaphysis clamp 35 allows to secure thefixation device to bone screws implanted in the proximal or the distalend portions of a tibia, or implanted in the distal end portion of afemur.

[0040] The metaphysis clamp 35 is held in one of the clamps 5 or 6, inthe same way as the connecting member 31. In fact, the metaphysis clamp35 would include, as same as the connecting member 31, a cylindricalshank 36 which fits in the cylindrical socket 17, and one end 37integrally formed with the shank 36 and perpendicularly extended to thelatter.

[0041] Such a end 37 is configured with a U-shaped portion which isintegrally formed with the shank 36, in eccentric position therefrom.Such a U-shaped portion basically comprises a pair of walls 38, 39extending parallel to and spaced from each other. A semi-cylindricalgroove 38′, 39′ is provided at the bottom of each wall 38, 39 on thesame side, which groove defines a semi-socket for accommodating acorresponding metaphysis bone screw, that is a screw implanted in theproximal or the distal end of a tibia, or the distal end of a femur, ina plane substantially perpendicular to the plane of the axis x-x.

[0042] Advantageously, the portion 37 includes means for clampingmetaphysis bone screws. This clamping means comprises a slider 50 whichis mounted on the portion 37 for sliding movement along a directionconcurrent to the direction in which the flange 26 is clamped againstthe wall 25.

[0043] Such a slider 50 comprises a rectangular base 49 formed with awindow 49 a, and has two plate-like lugs 51, 52 which are integrallyformed with the base 49 at the short sides thereof.

[0044] The plate-like lugs 51, 52 cooperate with the walls 38 and 39 toclamp the metaphysis screws therebetween. More particularly, the slider50 is sliding mounted on a narrowing end of the wall 39 through thewindow 49 a, such that the lug 51 is faced toward the portion 37 and ismovable between the walls 38 and 39, parallel thereto.

[0045] At the free ends of the lugs 51 and 52, and on the same side areprovided respective semi-cylindrical grooves 51′, 52′, each defining asemi-socket accommodating a corresponding metaphysis bone screw. Withthe slider 50 assembled to the portion 37, the grooves 38′ and 51′ faceto each other, and so do the grooves 39′ and 52′, ready for clampingonto a corresponding metaphysis screw.

[0046] A locking screw 53 passes through a hole laterally formed in theslider 50 and engages in a threaded hole formed close to the free end ofthe wall 39 for locking the slider 50 in place, clamping onto themetaphysis screws.

[0047] In this way, i.e. with the screws, including the side onesbetween the wall 25 and the flange 26, and the metaphysis ones betweenthe slider 50 and the portion 37, all brought to a tightened state bydisplacements occurring all in the same direction, their mutualpositions are retained even when their diameters change, for example,from screws with a diameter of 6 mm to screws with a diameter of 8 mmthroughout.

[0048] The fixation device of this invention does solve the technicalproblem and offers a number of advantages, among which the foremost isthat the clamps are of universal utility, unlike prior solutions.

[0049] In fact, the middle body 2 can have opposite clamps associatedwith it, which serve different functions but stem all from a commonbasic structure.

[0050] Furthermore, the fixation device made of a transparent materialto X-radiation allows the orthopedic surgeon to radiograph the affectedregion without suffering interference from bulky objects.

[0051] Also, it should be noted that the middle body accounts for amajor portion of the overall length of the fixation device according tothe invention, and allows the fixator length to be adjusted for almostany traumatic situations.

[0052] It should be further noted that the multiple impressions producedby the contrate teeth in the surface of the ball head, so that inpractice the ball-and-socket joint can be locked in any desired angularposition, also forbid re-use of the clamps, which are thereforedisposable clamps. This offers an additional advantage from both thesanitary and the safety standpoints.

1. A disposable axial external fixation device for reducing bonefractures, of the type comprising an extendible rod-like middle body (2)and oppositely located bone screw clamps (5,6) which are articulated torespective ends (3,4) of the rod-like middle body (2) by means of balljoints, characterized in that a ball-and-socket joint (16) is mounted toeach clamp (5,6), within a main body (20), and that locking means (40)of the ball-and-socket joint (16) in a selected angular position isprovided through a permanent set of the ball-and-socket joint.
 2. Anexternal fixation device according to claim 1, characterized in thatsaid ball-and-socket joint (16) comprises a cylindrical socket (17)formed in the main body (20) of the clamp (5,6), and a ball head (18)received in the cylindrical socket (17), and in that said locking means(40) is guided for movement in said socket toward and away from saidball head (18).
 3. An external fixation device according to claim 2,characterized in that said locking means (40) comprises a slider (41)which is guided for movement toward the ball head (18) within thecylindrical socket (17) of the main body (20), by the action of drivingmeans (42), for locking said ball head (18) in a positive manner.
 4. Anexternal fixation device according to claim 3, characterized in thatsaid slider (41) comprises a plurality of contrate teeth (44) projectingtoward a same direction.
 5. An external fixation device according toclaim 4, characterized in that said contrate teeth (44) are adapted tobite into the surface of the ball head (18) and form a plurality ofimpressions to a suitable depth therein.
 6. An external fixation deviceaccording to claim 3, characterized in that the driving means (42)comprises a shaft (47) transversely extending to the cylindrical socket(17) and provided with a cam (47 a) acting on the slider (41).
 7. Anexternal fixation device according to claim 5, characterized in thatsaid shaft (47) is manually rotatable with the aid of an appropriatewrench, and is formed with an embedded hexagon (43) at an accessibleend.
 8. An external fixation device according to claim 5, characterizedin that it comprises means (45) for limiting the rotation of said shaft(47), the means (45) comprising a radial nose (46) integrally formedwith the shaft (47) and appearing externally of the main body (20), saidradial nose being adapted to abut against a stop (48) formed on the mainbody (20) at an appropriate angular setting of the shaft (47) relativeto the main body (20).
 9. An external fixation device according to claim1, characterized in that said clamps (5,6) are made out of a transparentmaterial to X-radiation.
 10. An external fixation device according toclaim 1, characterized in that it further comprises an ancillary member(30) releasably associated with the free end of a clamp (5,6) to enableits connection to another fixation device or to other bone screws. 11.An external fixation device according to claim 10, characterized in thatsaid ancillary member (30) is rotatably mounted in said cylindricalsocket (17) at the free end of said main body (20).
 12. An externalfixation device according to claim 11, characterized in that theancillary member (30) comprises a cylindrical shank (32) inserted intosaid cylindrical socket (17), and a portion (33) transversal to theshank (32) and integrally formed with the latter.
 13. An externalfixation device according to claim 10, characterized in that saidancillary member (30) comprises a cylindrical shank (36) inserted intosaid cylindrical socket (17), and a metaphysis clamp (35) connected tosaid shank (36).
 14. An external fixation device according to claim 13,characterized in that said metaphysis clamp (35) comprises means(37,38,39,50,51,52,53) for clamping metaphysis screws having movingparts which are movable in the same direction as the moving parts ofmeans (25,26,21,22,23) for clamping bone screws.